fix: Upgrade testcontainers dependency to 0.15.1 (#75)

We seem to be experiencing flaky builds on datahub (CI/CD fails on PRs: e.g. https://github.com/linkedin/datahub/pull/2084/checks)
specifically:
Execution failed for task ':gms:impl:integrationTest'

and the root cause seems to be: testcontainers/testcontainers-java#3574

Upgrading to 1.15.1 hoping that this fixes it 🤞

build.gradle

@@ -62,8 +62,8 @@ project.ext.externalDependency = [
     'reflections': 'org.reflections:reflections:0.9.11',
     'rythmEngine': 'org.rythmengine:rythm-engine:1.3.0',
     'spock': 'org.spockframework:spock-core:1.3-groovy-2.4',
-    'testContainers': 'org.testcontainers:testcontainers:1.15.0',
-    'testContainersJunit': 'org.testcontainers:junit-jupiter:1.15.0',
+    'testContainers': 'org.testcontainers:testcontainers:1.15.1',
+    'testContainersJunit': 'org.testcontainers:junit-jupiter:1.15.1',
     'testng': 'org.testng:testng:6.9.9'
 ]